Lunar L1 Gateway

1
Lunar L1 Gateway SEP Design Briefing

• Gateway
• Element Lead Frank Lin
• Lead Systems Engineer Jim Geffre
• JSC Gateway Design Team
• SEP
• NASA GRC SEP Team
• 11/2/01

2
Briefing Objectives

• Review work done to date by JSC Advanced Design
  Team on Gateway architecture
• Focus on design of Gateway Element
• Review work done to date by NASA GRC on Gateway
  architecture
• Focus on design of Solar Electric Propulsion
  (SEP) system

3
Briefing Outline

• Gateway Architecture Overview
• Gateway Mission Overview
• Requirement Development
• Mission Requirements and Constraints
• Functional Allocation Matrix (FAM), N2 Charts,
  Sub-system Requirements
• Gateway Sub-Systems Descriptions
• Preliminary Hazard and Reliability Analysis
• Future Technology Investments
• Open Issues/Forward Work
• Solar Electric Propulsion

4
Gateway Architecture
GPS Constellation
Earths Neighborhood
Crew departs from and returns to ISS
L1 Gateway
Lunar Habitat
Lunar Lander
Crew Transfer Vehicle

• Crew Transfer Vehicle
• Transports crew between ISS and Gateway
• Nominal aerocapture to ISS, or direct Earth
  return contingency capability

• L1 Gateway
• Gateway to the Lunar surface
• Outpost for staging missions to Moon, Mars and
  telescope construction
• Crew safe haven

• Lunar Lander
• Transports crew between Gateway and Lunar Surface
• 9 day mission (3 days on Lunar surface)

• Lunar Habitat
• 30-day surface habitat placed at Lunar South Pole
• Enables extended-duration surface exploration and
  ops studies

5
Gateway Mission Profile
Launch Gateway on DELTA IV-H
Activate Critical Systems, Inflate Checkout
Gateway
LEO Operations
Launch Shuttle with Gateway Outfitting Crew
Shuttle Rendezvous and Docking with Gateway
Outfit Checkout Gateway
SEP Autonomously Dock with Gateway
Autonomously Deploy SEP Solar Arrays
Launch SEP on DELTA IV-H
Gateway and SEP spiral to LL1 (unmanned)
Up to 15 days
Lunar Surface Mission
Crew Arrives at Gateway in CTV
Crew Returns to Earth in CTV
30 days
LL1 Operations
Telescope Mission
Deliver Lunar Lander to Gateway (unmanned)
30 days
Gateway Logistics Resupply / Cargo Delivery
(unmanned)
Science Mission
Reflects crew time spent in Gateway
6
Gateway Mission Flow Chart
Send replacement/repair mission on Shuttle
Launched on Delta IV
Stable on-orbit config
Inflate, activate, and checkout in LEO
All systems go?
Y
N
N
Y
All systems go?
Shuttle outfitting in LEO, final Checkout
(detailed list TBD)
Done
N
N
N
Y
Y
Y
SEP Rndz/ dock with Gateway at LEO
Fully deploy SEP arrays
Launch SEP stage
Partial SEP array deploy
Shuttle returns
Y
Y
N
Attempt repair on later Shuttle mission if
possible
N
Stabilize Gateway and SEP
N
Y
Lunar lander
Lunar mission

Gateway uses chem prop system for separation
and L1 insertion
Config Gateway for stable L1 ops
CTV
Transit from LEO to LL1
SEP stage undocks for return
Telescope arrives
Telescope mission
CTV
Refer to Lunar L1 Architecture Operational
Events Flow Chart
7
Requirements and Constraints

• Top Level Requirements
• Stage telescope construction and lunar surface
  missions from Gateway
• Two telescope construction missions per year
• Two lunar surface excursions per year
• Support crew of four
• Design lifetime of 15 years
• Simultaneously support three docked vehicles
  (CTV, Lunar Lander, Logistics Module)
• Provide EVA capability for nominal operations
• Maintain position at lunar L1 Lagrange point
• Autonomous transfer from low-Earth orbit to lunar
  L1
• Design Goals and Constraints
• Incorporate inflatable technology
• Delivery to lunar L1 via solar electric
  propulsion
• Crew safety is highest priority
• Maximum system technology demonstration
  capability
• Maximize use of technologies viable for future
  human space exploration

8
Gateway Requirement Development Process
FAM
N2 Chart

• Defines System interface connectivity for
  Gateway by mission phase
• Defines type and disposition of system
  interfaces

• Defines Gateway functions for each mission
  phase
• Identifies Gateway Sub-systems for each mission
  phase

Sub-system Requirements

• Defines required systems for each mission phase

9
Gateway Element Summary
Inflatable Airlock (4)

• Element Design Lifetime 15 yrs
• Element Mass
• Launch 22,827 kg
• Outfitting 588 kg
• Post-outfitting 23,415 kg
• Resupply mass/Volume
• 6-months 805 kg / 3.878 m3
• 24-months 2,824 kg / 7.587 m3
• Element Volume
• Launch 145 m3
• Operational 275 m3
• Power provided
• PV Array 12 kW Nom/14.4 kW Peak
• Energy Storage
• Batteries 71 kW-h
• Flywheel 20 kW-h
• Support Missions
• Outfitting at LEO One mission/architecture
• HFH consumables Two missions/year

Radiators (3)
ACS
Cupola
RCS jets
Prop ECLS tanks
EVA Work Platform/ Telescope Assembly Site
P/V Arrays (2)
RMS
10
Gateway Configurations
LEO, Transit, L1 Stand-by Configuration
Launch Configuration
Telescope Operations Configuration
Lunar Operations Configuration
11
Gateway Systems

• Attitude Control System (ACS)
• Avionics
• ECLSS
• EVA
• Human Factors Habitability (HFH)
• Power
• Propulsion
• Robotics
• Structures
• Thermal Control
• Mission Operations
• Mission Success

12
Attitude Control System Design Summary

• System Requirements
• Maintain Solar Inertial Attitude for Gateway in
  low-Earth orbit and at Lunar L1
• Provide 1,000 N-m-s of Momentum Storage
• Provide 20,000 W-hr of Energy Storage
• Assumptions Made
• Momentum storage requirements are equivalent to
  NGST
• Flywheel system axis must be aligned with one of
  the Gateways body axes
• Concept Trades Considered
• Flywheels
• Control Moment Gyros
• Chemical RCS
• Selected Technologies
• Integrated Power and Attitude Control System
  (IPACS) Flywheels
• Rationale The flywheel system offers the
  potential for a coupled energy storage and
  attitude control capability, and is the least
  mass alternative. A CMG system would require a
  larger lithium-ion battery system to accommodate
  the extra 20 kW-hr of energy storage. Chemical
  RCS requires a large propellant load to handle
  the attitude control needs for 15 years.

13
Attitude Control System Design Summary

• System Specification
• Physical dimensions Mass 318 kg Volume
  0.288 m3
• Provide 70 kWe peak power to user
• TRL 3
• Issues and Concerns
• None
• Forward Work
• Determine flywheel system reliability lifetime

IPACS Flywheel System
14
Avionics System Design Summary

• System Requirement
• Provide guidance, navigation, control,
  communications, and health monitoring of Gateway
• Assumptions Made
• Communications would follow proposed Ka-band
  upgrade and operate in the 32ghz range
• UHF would be used for space-to-space
  communication between vehicles
• Flight Computer System would be a quad-redundant
  system based on the X-38 Fault
• Tolerant Processor model
• The flight computer, itself, would be based on
  the Universal Mini-Controller (UMC)
• Flight Computers would be distributed so that
  they could also collect data from subsystems
• near their respective locations
• Wiring would include a combination of fiber
  optics, wireless, and parasitic use of the power
  
• buses where applicable, optimally selected to
  minimize mass and maximize reliability
• Concept Trades Considered
• NA

15
Avionics System Design Summary

• System Specification
• Mass is 251kg
• Total Volume Required 1.0 m3
• Overall Sub-system TRL Level 6
• Issues and Concerns
• None
• Forward Work
• None

16
Avionics System Design Summary
Ka-band Antennae
Gateway Avionics Architecture

Omni
Antenna Switch
Antenna Switch
Video
PAU
Video System
Digital Voice
Displays
SSVR (UHF)
Ka-Band
Data Buses
Power Amplifier
Power Amplifier
LDR
Flight computers
INS
Crew Interface - Hand Controllers - Switches
HDR
Sensor Data
Intercomputer Bus
HDR and LDR Data
17
ECLSS System Design Summary

• System Requirement
• Control cabin temperature, humidity
  (NASA-STD-3000), and pressure (select at 9 psia)
• Provide crew consumables (O2, N2, H2O) for
  cabin, airlock and EVA
• Provide closed air, water recovery and waste
  management systems to minimize re-supply
• Assumptions Made
• Two-year re-supply period
• Crew daily O2 consumption rate - 0.84
  kg/person/day
• Crew drinking and food preparation 2.8
  kg/person/day, hygiene, 6.8 kg/person/day
• No dishwasher, no laundry, no salad machine
• Concept Trades Considered
• High pressure vs. cryogenic N2 and O2 storage
• CO2 removal technology 4 x BMS vs. solid amine
• Biological water recovery technology (BWR) vs.
  Vapor Phase Catalytic Ammonia Removal technology
  (VPCAR)
• Selected Technologies
• Cryogenic w/ High pressure for Rationale
  Cryogenic system has less mass. High inflation
  pressure tanks for initial Gateway inflation
  for shorter inflation time.
• 4 x BMS CO2 removal system Rationale relative
  mature close CO2 removal system
• VPCAR Rationale Mass, volume and power
  benefits. Shorter
• turn-around time. Restart ability.

18
ECLSS System Design Summary

• System Specification
• ECLSS System Mass 2851 kg
• Dry Mass 2174 kg
• Fluid Mass 677 kg
• ECLSS System Volume 15.9 m3
• TRL Level
• CO2 removal 9
• Oxygen generation system 6
• CO2 reduction system 6
• CO2 compressor 3
• Trace contaminant control 4
• Issues and Concerns
• NASA-STD-3000 set long-term mission spacecraft
  pressure at 14.5 14.9 psia.
• Forward Work
• Report

• Fire detection and suppression 9
• Vapor Phase Catalytic Ammonia Removal (VPCAR) 4
• Water recovery from brines (air evaporation
  system) 6
• WRS product water post processor (ion-exchange
  beds) 6
• Solid Waste Processing (Lyophlilization water
  recovery) 3

19
ECLSS System Design Summary
ECLSS Water Recovery System Block Diagram
Respiration, condensate
Potable Water Tank
Urine flush water
VPCAR
Hygiene wastewater
Food preparation
45 kg/day
brine
vacuum
Cond HX
vent
CH4,CO2,H2
air
Sabatier CO2 reduction subsystem
ECLSS Air Revitalization System Block Diagram
4BMS
CO2
TCCS
H2O
H2
O2
O2 Gen. subsystem
Waste Processing System
Cabin at 9.0 psia O2 30 N2 70
Air leaks
O2 Tank
N2 Tank
O2 from propulsion cryogenic storage
Water from water recovery system
High Pressure
20
EVA System Design Summary

• System Requirement
• Store 4 Space Suits from CTV
• Support Four six month mission phases prior to
  resupply
• 10 EVAs (8 hr) for Telescope mission for four
  missions
• Gateway maintenance at one EVA per six month
  mission
• Total of 84 4 hr EVAs prior to resupply
• Assumptions Made
• 10 EVAs for Telescope mission
• 1 EVA for Gateway maintenance per six month
  mission
• Two tool boxes for Telescope assembly
• Concept Trades Considered
• Recharge system to recharge 3000 psi PLSS Oxygen
  tanks from low pressure cryo tanks
• Chose thermal compression to 850 psi, mechanical
  compression from 850 psi to 3000 psi, (ORCA),
  ECLSS emergency repress tank used as accumulator
  for rapid refill then recharged using compressor.
• System Specification Dry Mass Volume Minimum TRL
• Space Suits 636 kg 3.62 m3 TRL 2
• Vehicle Support for EVA 212 kg 0.34 m3 TRL 3
• EVA Translation Aids 123 kg 3.36 m3 TRL 9
• EVA Tools 132 kg 0.2 m3 TRL 9
• Airlock 433 kg 8.18 m3 TRL 3

21
EVA System Design Summary

• Issues and Concerns
• Lack of Technology Development Funds to raise low
  TRL items within schedule needs
• Forward Work
• Light weight PLSS
• Recharge system to recharge 3000 psi PLSS tanks
  from 150 psi lox supply

22
Gateway EVA System Block Diagram
23
Habitability and Human Factors (HFH) System
Design Summary

• System Requirement
• Provide consumables for 60 days
• Provide a minimum habitable volume of 60 m3 (15
  m3/person)
• Comply with MSIS/NASA-STD-3000
• Assumptions Made
• Maximum contingency duration of Gateway use is
  60 days, with a 25-day crewed maximum nominal
  mission phase.
• Gateway station provides an oasis in terms of
  living environment
• Concept Trades Considered
• Crew Quarters Dorm Style v. Private Quarters
• Waste Collection Facility Plumbed v.
  self-contained facility v. bags only
• Hygiene Facility Partial-body cleansing v.
  Full-body cleansing
• Medical Equipment Med kit only v. nominal
  mission life support v. contingency scenario
  life support
• Exercise Capability No exercise v. limited
  resistive v. cardio only v. resistive and
  cardio training
• Food System Shuttle food system (pure-ambient)
  v. Conditioned food
• Clothing Clothing as consumable v.
  washer/dryer
• Acoustics Acoustic abatement throughout module
  v. Acoustic abatement at CQ and equipment room
  hatch only

24
Habitability and Human Factors (HFH) System
Design Summary

• System Specification
• Mass 2507.48 kg
• Volume
• HFH equipment 15.04 m3
• Habitable volume 200 m3
• TRL Level 8
• Issues and Concerns
• Conditioned food This is a nutritional need for
  the health of the crew, but is currently not
  considered feasible because of infrequent
  resupply missions to the Gateway/radiation issues
• Windows Additional viewing windows (for
  scientific observation and recreation) are
  preferable in the Gateway
• Resupply Logistics of resupply of
  crew-preference and crew-specific items (e.g.
  clothing, food, hygiene consumables) needs to be
  more well-defined with consideration for
  radiation exposure
• Forward Work
• Research possible HW mass losses between now
  (current Station hardware) and fly date
• Double check depressurization compatibility of
  HW and supplies
• Continue modifying detailed layout
• Research exercise technologies
• Research food technologies
• Investigate lighting effects and simulated
  windows

25
Habitability and Human Factors (HFH) Cabin Layout
SMF
HDTV
Stowage
Exercise Facility
CQ
CQ
Galley
Workstations
HF
CQ
WCF
CQ
CQ Crew Quarters HF Hygiene Facility WCF
Waste Collection Facility SMF Space Medical
Facility HDTV High Definition TV
Stowage
26
EPS System Design Summary

• System Requirements
• Provide 1kW (Peak) during ascent, orbit injection
  and deployment for Gateway survival and initial
  on-board operations.
• Provide 2KW during LEO operations (90 min. orbit
  with 45 min. eclipse time) prior to rendezvous
  with SEP.
• Provide continuous 12 KW while at LL1 with an
  energy storage capability to compensate during
  the 13 hr maximum eclipse time every 6 weeks for
  the entire Gateway life cycle of 15 years.
• Assumptions Made
• Power generation and storage sized to include 30
  contingency and 20 additional mass for secondary
  support structure.
• It assumed that the overall EPS system is about
  70 efficient (user power/power generated)
• Arrays 1 fault tolerant, but rest of H/W 2 fault
  tolerant (ring bus architecture assumed).
• High voltage DC to be provided by array and
  batteries and distributed within the Primary
  Distribution System.
• Secondary Distribution System is 115 Vac, 3Ø,
  400 Hz
• Two Tertiary Distribution Systems included 28
  Vdc and 110Vac, 1Ø, 60Hz.

27
EPS System Design Summary

• Concept Trades Considered
• Ultraflex vs. Inflatable PV Array
• Thin-film vs. Fiber Li-Ion Battery
• 28 Vdc vs. 115 Vac, 3Ø, 400Hz
• Selected Technologies
• Ultraflex, Fiber Li-Ion integrated into
  structure, 115AC, 3Ø, 400Hz
• Rationale Lower mass and design simplicity
• System Specification
• Physical dimensions Mass 1,335 kg Volume
  27 m3
• Provide 12 kW nominal with 14.4 kW Peak to user
• Arrays capable of 20.7 kWe
• TRL
• PV Arrays 7
• Deployment Truss 6
• Battery 2
• Wiring Harness 9
• PMAD 6
• Issues and Concerns
• Development of 400 Hz RPC Box

28
EPS System Architecture
Charge / Discharge Unit 1
Charge / Discharge Unit 1
Fiber Li-Ion Fabric Section
Representation of a Single String of the Inner
Loop Power Distribution System
Fiber Li-Ion Fabric Section
UltraFlex Array Unit 1
UltraFlex Array Unit 2
Bus B
Bus C
Bus A
Relays
155 Vdc
RPC Box
INVERTER
Inverter
Inverter
Inverter
RPC Box
RPC Box
115 Vac, 3Ø, 400 Hz
INVERTER
INVERTER
Secondary Distribution System
RPC
RPC
RPC
Relays
Fiber Li-Ion Fabric Section
Fiber Li-Ion Fabric Section
Charge / Discharge Unit 2
Charge / Discharge Unit 3
Power Bus 3
Power Bus 2
Tertiary Distribution System
Power Bus 1
Charge / Discharge Unit 2
Charge / Discharge Unit 3
110 Vac, 1Ø, 400 to 60 Hz Frequency Converter
115 Vac, 3Ø, 400 Hz to 28 Vdc Converter
EPS System Block Diagram
Primary Distribution System
29
Propulsion System Design Summary

• System Requirement
• Provide Gateway vehicle with approx. 50 m/s
  delta V per year for station keeping
• Assumptions Made
• Propellant resupplied once every two years
• Vehicle lifetime 15 years
• Propulsion system for station keeping only, no
  ACS
• Book-keep ECLSS and EVA O2 (491 kg)
• Concept Trades Considered
• Propellant selection -Tridyne, Hydrazine,
  NTO/MMH, LOx/CH4
• System size vs. regularity of resupply
• Concept(s) Selected
• 12 x 110 N LOx/CH4 engines Rationale
  Mass/volume savings, non corrosive exhaust
  products
• System Specification
• Mass 176 (dry) kg. 1,444 (total) kg.
• Dimensions/Volume Approx. 1.23 m3 tank

30
Propulsion Preliminary Design Summary

• Issues and Concerns
• Thruster placement due to the nature of the
  inflatable structure design and plume impingement
  on solar arrays
• TRL
• Engines 4
• Cryocoolers 4
• Forward Work
• None

31
Propulsion Preliminary Design Summary
Integrated LO2/LCH4 Gateway Propulsion Schematic
110 N RCS Engines 322 s Isp 3.8 MR
TVS
32
Robotics System Design Summary

• System Requirement
• Support EVA activities and maintenance,
  inspection and mobility of both intra- and extra-
  vehicular systems
• Assumptions Made
• Large arm needed for gross payload manipulation
• Dexterous robot needed for human-equivalent
  manipulation
• Will use automated smart systems where
  appropriate
• Concept Trades Considered
• No tasks or requirements were identified that
  required a trade study
• System Specification
• Robotic Manipulator System
• Mass 543 kg
• Dimensions/Volume Arm- 15.2 m x Æ.33 m
• RWS Stowed- ISPR 1.01 m x 1.07 m x 1.98 m
• TRL Level Arm- 9
• RWS- 8
• Robonaut
• Mass 136 kg
• Dimensions/Volume .71 m³
• TRL Level 5

33
Robotics System Design Summary

• Issues and Concerns
• Current work reflects generic robotic
  requirements defined as
• Gross payload manipulation
• Human-equivalent manipulation
• Forward Work
• Continue development of Robonaut to increase
  autonomy and functionality
• Define and identify the robotic requirements
  associated with telescope construction
• Size RMS based on telescope construction
  requirements

34
Robotics System Design Summary
Available Solutions
35
Structures System Design Summary

• Structural Requirements
• Interface to Delta IV Heavy
• Support crew of 4 for 25 days
• Provide docking mechanisms for CTV and Lunar
  Lander
• Provide worksites for constructing/assembling
  telescope
• Provide structure to mount other systems within
  primary structure
• Assumptions Made
• 6 g axial and 2.5 g radial launch loads
• 9 psi nominal internal pressure
• Concept Trades Considered
• Hardshell vs. Inflatable vs. Hybrid Gateway
  Structure
• Hybrid structure encouraged by architecture team
  for future applicability to future exploration
  missions
• System Specification
• Gateway total Mass 7354 kg
• Overall length 9.3 m
• Hard shell Dia. 4 m
• Inflatable Dia 9 m

36
Structures System Design Summary
37
Structures System Design Summary

• Issues and Concerns
• Radiation protection not incorporated into
  design due to unavailable design support from SF2
• Material properties for the mission at L1 are
  assumed to be acceptable at EOL for the mission
  duration.
• Procedure for replacing MM/OD shielding on
  inflatable not identified
• Forward Work
• Incorporating radiation protection
• More detailed design and analysis of primary
  structure

38
TCS System Design Summary

• System Requirement
• Collect, Transport, and Reject 15.6 kW to space
• Provide heaters to maintain low temperature
  limits of the Gateway shell
• Assumptions Made
• Radiators are freeze tolerant
• All radiator panels see deep space environment
• Air distribution over the internal inflatable
  wall prevents condensation (no heaters on fabric)
• Concept Trades Considered
• Single Loop vs. Dual Loops
• TCS working fluid types
• Flow Through Radiators vs. Heat Pipe Radiators
• Number of Radiator panels
• Concepts Selected
• Single loop Rationale Less hardware, no
  toxic fluid needed
• 60 propylene glycol/40 water Rationale
  Freeze tolerance, safer working fluid
• Flow through radiators Rationale Lower mass

39
TCS System Design Summary

• System Specification
• 663 kg Total Mass
• 115.4 kg Fluid mass, 547.6 kg Dry mass
• 3.39 m3 Total Volume
• 0.84 m3 ETCS Radiators, 2.56 m3 Multi-layer
  Insulation
• TRL levels
• Flow through, flexible, freeze tolerant
  radiators 4-5
• All other TCS components 9
• Issues and Concerns
• Working fluid concerns regarding freeze
  tolerance
• Will single loop architecture function in the
  environment
• Inflatable inner wall air flow
• Exposure of equipment in inflatable section to
  space vacuum
• Equipment operation at 9.0 psia operating
  pressure
• Forward Work
• More detailed analysis to characterize the
  thermal environment
• Evaluate test data for flexible radiators and
  heat pipes

40
TCS System Block Diagram
Redundant Pumps
41
Mission Operations Assessment

• Gateway checkout in LEO
• Critical Gateway systems to be checked out prior
  to Shuttle outfitting mission
• Pressure vessel integrity
• Life support system
• Electrical power system
• GNC/attitude control system
• Data processing
• Communication system
• Thermal control system
• Remaining systems will be checked out during
  Shuttle outfitting mission and prior to transfer
  to Lunar L1
• Robotics
• Waste collection system
• HFH
• Inflatable airlocks
• LEO Outfitting Mission
• Pressurized cargo carriers considered
• MPLM, SpaceHab module
• Recommendation
• Modify double SpaceHab with IBDM

42
Mission Operations Assessment

• Gateway Resupply strategy
• Immediate resupply
• CTV to carry immediate crew resupply items
• Limited volume and mass items
• CTV to leave contingency food on Gateway
• CTV to swap out shelf life sensitive items that
  are common on CTV and Gateway
• Medical supplies, food, etc.
• Short term resupply
• Once every six months
• Use Lunar Lander habitable volume for stowing
  resupply items
• Resupply items include Food, clothing, medical
  supplies (items that are less time and radiation
  sensitive), misc. crew supplies, etc.
• Long term resupply
• Once every two years
• Require a module capable of carrying pressurized
  and unpressurized cargo
• Identified as a new element to the Gateway
  architecture.
• Resupply items include Station keeping
  propellant, ECLSS system consumables, large ORUs
  and tools, experiments, etc.

43
Safety and Mission Assurance Strategies for
HumanExploration Gateway II PHA Summary
Category Eliminated Controlled Accepted Risk Open
Hazardous Causes Identified 0 77 0 2

• Open Work from Hazard Analysis
• An analysis of the radiation protection of the
  vehicle's final configuration should be done.
  This will affect the hazard controls for two
  conditions identified concerning excessive
  radiation in the crew habitable environment.

44
Gateway Sparing Analysis for Avionics Subsystem
45
Gateway, SEP and Suit Reliability
46
Conclusions

• System Reliability Sparing
• Reliability Block Diagram Analysis predicted a
  Gateway reliability with no repair of
  approximately 72. This reliability is
  associated with mission success modeling of all
  the supporting subsystems which includes EVA
  suits for telescope construction.
• Sparing requirements for one re-supply cycle
  (10,225 hours) of the Gateway will be significant
  given the reliabilities of the modeled
  subsystems.
• Crew Safety
• The PHA has documented the subsystem design
  mitigations controlling the hazards identified.
• All subsystems will meet fail-op/fail-safe
  requirements as specified in the Human Ratings
  Requirements with the option of the LTV ticket
  back to LEO. This however only applies to crew
  safety and not mission success.
• Open Work Analysis to evaluate the inherent
  radiation protection of the Gateway design

47
Gateway Mass Summary
Mass Limit 35,400 kg (Delta IV Heavy Capability)
48
Gateway Power Profile
49
Gateway Cost Summary
Gateway 979.1 M
STR MECH 453.8 M
EVA 5.1
Propulsion 87.9 M
Power 59.1 M
Avionics 50.8
ACS 31.3
To Be Updated
Systems Integration Test 59.2 M
Thermal Control 62.2 M
Human Factors Habitability 0.45 M
ECLSS 130.2 M
Robotics 104 M
PRICE H Cost Analysis Assumptions

• All masses and volumes are entered in metric
  units
• Cost estimates are shown in 2001 dollars
• Cost includes hardware development and
  manufacturing
• Assume three prototype for each system ?2
  prototype / flight unit
• Year of technology (YRTECH)?value is 2005

• Development start date(DSTART)1/02
• Completion date of first prototype (DFPRO)4/07
• Completion date of last proto/flight unit
  (DLPRO)4/09
• Twenty percent program reserve added to PRICE-H
  cost figures
• Does not include recurring or operations costs

50
Future Technology Investments

• ACS
• Flywheel technology
• ECLSS
• Vapor Phase Catalytic Ammonia Removal (VPCAR)
• Lyophilization Water Recovery
• EVA
• Inflatable Airlock
• Next Generation Space Suit
• EPS
• Fiber Li-Ion Batteries
• Propulsion
• Cryo Cooler
• Structures
• Radiation Protection Materials and Methods
• MMOD Protection Materials and Methods

51
Open Issues / Forward Work

• No radiation protection analysis
• Unknown long-duration material degradation in
  Lunar L1 environment
• Unknown effects of multiple spirals through Van
  Allen radiation belts
• Need a detailed orbit propagation to determine
  exact station-keeping requirements
• Resupply vehicle design unknown
• Gateway trash disposal
• Need better definition of telescope mission
  requirements to complete design of Gateway
  systems
• Examine rigid structure design for comparison
  to current inflatable concept

52
Lunar L1 Gateway Mission ArchitectureSolar
Electric Propulsion (SEP) Stage Preliminary
Configuration Summary of Oct. 12, 2001
Presentation

• NASA Glenn
• Tim Sarver-Verhey
• Tom Kerslake
• Len Dudzinski
• Leon Gefert
• Janice Romanin
• Robert Sefcik
• Dave Hoffman
• October 25, 2001

53
Gateway Solar Electric Propulsion (SEP) Stage

• System Requirements
• Launch on a Delta IV Heavy or Shuttle to 400 km
  28.5 LEO1
• Exploration Class Delta IV Heavy presumed - 35
  MT to LEO
• 30 MT payloads 2
• Lander Habitat mass
• 35 MT Total SEP Stage Mass Limit
• Derived from requirements 1
• Maximum 6-month LEO-to-Lunar L1 trip time 2
• A 30 MT Lander must be delivered to Lunar L1
  every 6 months
• TRL 6 by 2005 for all systems technologies1
• Assumptions Made
• Structural electrical interfaces with SEP stage
  payloads
• 5 kW power transfer from SEP stage to Gateway
  Habitat payload
• 12 m maximum Gateway Habitat payload diameter x
  10 m length
• SEP stage housekeeping power 1 of total power
  required
• 20 SEP stage dry mass margin
• Sources
• 1Lunar L1 Gateway Introduction Package, J.
  Geffre, 7/9/01
• 2Lunar L1 Architecture Timeline, email from
  J. Geffre, 7/27/01

54
Gateway Solar Electric Propulsion (SEP) Stage

• Primary Issues/Trades Considered
• What is the power required vs. trip time?
• To deliver 30 MT to L1 in 180 days, a 584 kW SEP
  stage with 15.0 MT dry mass and 20.0 MT of xenon
  propellant is required - assuming 2,700 s (Isp).
• What is the cost?
• 1B Total SEP Stage Cost (521.5M DDTE
  435.1M Flight Unit) (FY01 ).
• Should the SEP stage remain attached to the
  Gateway Habitat?
• No better to re-use the stage since its excess
  power is not needed its large deployed array
  area would impact Gateway Habitat field-of-view
  and work areas.
• How many times can/should an SEP stage be reused?
• At least 2 roundtrip transfers per SEP stage are
  feasible by oversizing the solar arrays and
  assuming LEO replacement of the electric thruster
  and xenon and A/C system fuels pallets is
  possible.
• Should solar array pointing be solar inertial or
  articulating?
• Inertial solar arrays have significant vehicle
  operations mass advantages reduces array area
  mass, reduces structural dynamic impacts
  associated with articulation, allows constant
  power Hall Thruster operation, thruster boom
  provides isolation needed to mitigate thruster
  plume impingement.

55
Gateway Solar Electric Propulsion (SEP) Stage
System Specification Initial conceptual design
sizing highlightssubject to further revision!

• Features
• 180-day trip time, 400 km 28.5 LEO to Lunar L1
• 46-day return, Lunar L1 to 400 km 28.5 LEO
• 584 kW SEP Stage Power (supports 2 round trips)
• 7,300 m2 High-Voltage Thin-Film Solar Array (2
  wings)
• 12 Direct-Drive Hall Effect 50 kW Engines (incl.
  1 spare)
• Mass Characteristics
• 15.0 MT SEP Stage Dry Mass (incl. 20 margin)
• 20.0 MT Xenon propellant
• 30.0 MT Payload
• 65.0 MT Vehicle Initial Mass LEO

15.0 MT SEP Stage Dry Mass Total, incl. margin

1.87 Hall Engines PPUs
0.13 Thruster Pallet Gas Manifold
0.15 PPU Thermal Control
1.97 Articulated Boom, incl. power, fluid data lines
1.21 Xenon Pallet
1.71 Xenon Tanks
0.59 SEP Base Structure
0.41 PMAD Cables
0.30 Attitude Control System
0.63 Thermal Control System
0.43 Energy Storage System (Li-ion Batteries)
2.93 Solar Array Assemblies
0.03 Guidance, Navigation Control
0.15 Command Data Handling
2.50 Margin (20)
56
Gateway Solar Electric Propulsion (SEP) Stage
Issues Concerns/Forward Work

• LEO refurbishment
• Remote/robotics or crew-tended?
• Thruster pallet replacement
• Xenon tank pallet replacement
• ACS propellant replacement/refill
• Large area array packaging deployment
• Dynamic analysis
• Stiffness requirements
• Type of thruster boom
• Deployable (SRTM) vs. rigid (ISS) or combination
• Stowage deployment of fluid power lines
• Dynamic analysis

• Attitude control subsystem refinement
• Impacts of thruster boom movements
• Impacts of large deployed area in LEO
• Momentum wheel ACS thruster propellant sizing
• Rendezvous docking with payloads
• Other subsystem sizing/refinement
• GNC
• CDH

57
Gateway Solar Electric Propulsion (SEP) Stage

• Thrusters (TRL 3/4)12 Direct Drive 50 kW Hall
  Effect Thrusters (HET)
• Xenon, 2500 - 2700 s Isp, 2.6 N thrust per engine
• 8500 hrs life
• 11 HETs required 1 spare
• HET mounted on replaceable 4m diam. thruster
  pallet
• Deployable Thruster Boom (TRL 7)
• 35m articulated boom for thrust vectoring (18.5 m
  deployable boom 8m inner outer rigid booms)
• Replaceable Xenon Tank Pallet (TRL 7)
• 4m diam x 4m cylinder (3 internal tanks)
• Photovoltaic Arrays (TRL 3/4) Two 3,750m2
  AEC-Able SquareRigger? style wings
• Thin-film cells (12 AM0 eff., 2006 target)
• SEP main body (4.5m diam x 1.5m) contains
• Array mechanisms
• Energy storage (Li-ion) power processing
• Attitude reaction control systems
• GNC and CDH systems
• Docking interfaces

Rigid Booms (at both ends of deployable boom)
Gateway Habitat Payload
Xenon Pallet
SEP Main Body
HET Pallet
Thruster Boom